This invention relates to surgical fasteners, e.g., anchors that secure sutures to bone, a meniscus, or other tissue. It further relates to a suture anchor that attaches a suture to tissue without the use of knots, and to methods of securing tissue using one or more anchors and a length of suture.
Many surgical procedures require the attachment of soft tissue, e.g., ligament or tendon grafts, to bone. This is typically accomplished by anchoring a suture in bone, for example with a screw, pin, or other bone anchoring device, and looping the suture around or stitching the suture to the soft tissue. When this process is completed, the surgeon generally must knot the suture to secure the tissue. This knotting process can be difficult and tedious, particularly during laparoscopic or endoscopic procedures, where the surgeon must remotely manipulate the suture using tools inserted through an endoscopic tube. Further, as many as six knots are often required to secure one suture. These knots may xe2x80x9cstand proudxe2x80x9d above the tissue and interfere with movement and healing.
One advance which has been proposed is the anchor apparatus disclosed by Goble, et al., in U.S. Pat. No. 5,702,397. That apparatus comprises an anchor body through which a suture passes, and which contains a clamping mechanism such as a spherical element within the anchor body. When the suture is pulled in a proximal direction, the clamp is urged into contact with the anchor body, thereby holding the suture in place. When the suture is pulled in a distal direction, the clamp disengages, and the suture can move freely through the anchor body. At least one end of the suture is stitched and/or knotted to soft tissue.
Several knotless suture anchor assemblies have recently been proposed by Thal in U.S. Pat. Nos. 5,569,306; 5,658,313; 5,665,112; and 5,683,419. These describe suture anchors which secure a filament having a small loop at one end. In some embodiments, another length of suture ends in a small block, which is passed through the loop to secure the tissue. While these structures can be secured without knots, the block used to secure the suture may itself stand proud above the tissue, causing discomfort and interfering with healing. In other embodiments, the anchor itself is passed through the small loop, creating a larger loop which is used to hold tissue.
U.S. Pat. No. 5,709,708, also by Thal, describes a suture anchor utilizing a continuous loop of suture material, which secures the tissue in a similar manner. As in the other Thal knotless anchors, the tension of the suture is dependent on the length of specially provided suture, which cannot be adjusted. Thus, these anchors cannot be used in surgical operations in which it is necessary to tighten a loop of suture to secure soft tissue.
The tying of suture knots presents difficulties in other surgical procedures, as well. For example, tears occur commonly in the menisci of athletes. The simplest method of repairing such a tear is to stitch it closed by passing a length of suture through the tissue and tying. However, the needles used in such surgery are very difficult to manipulate during endoscopic surgery, and the knots used to secure the suture may interfere with healing as described above. These difficulties are particularly severe in the restricted space of the joint capsule of the knee, a common location for such injuries. Other devices such as darts and clamps have also been proposed for this purpose; see for example U.S. Pat. Nos. 5,154,189; 5,269,783; and 5,702,462. Like suture knots, these devices may cause considerable discomfort during healing of the tear. Further, if made of non-bioabsorbable materials, a second surgery must be performed to remove the devices from the meniscus after healing.
A need thus exists for an improved technique and apparatus for securing tissues without the use of knots. A further need exists for such techniques and apparatus which also permit the position of the suture to be readily adjusted. A still further need exists for such apparatus which is small enough to avoid discomfort, which is amenable to fabrication from bioabsorbable materials, and which can be used either in bone or in soft tissue.
The above needs are among those met by the invention, which provides an anchoring device that can be embedded in bone or soft tissue, that permits suture length and/or tension to be readily adjusted, and that can be secured without the use of knots.
In one aspect of the invention, a suture anchor suitable to be embedded in bone has a cavity which holds a filament (e.g., a suture) by interference fit. The anchor holds the suture tightly enough to resist xe2x80x9coperationalxe2x80x9d forces to which the suture is subjected subsequent to deployment, e.g., during movement of the bones and/or soft tissues to which the suture is attached. However, the interference fit is weak enough to allow the suture to be pulled longitudinally through the cavity by a stronger force.
In use, such an anchor can be placed with some slack in the suture. The suture can then be tightened by pulling on one of its ends (with the larger force). It is an advantage of the invention that the tightening of the suture can be reversed, simply by pulling on a loop formed by the suture or by pulling on its opposite end. The suture does not loosen in normal use, however, since the forces required to move during deployment are greater than those exerted by the bones and/or tissues to which it is attached.
In a related aspect, the anchor may hold the suture at two points, forming a loop. The loop can be disposed around tissue and, then, tightened by pulling one end of the suture, thereby securing the tissue. Again, if the loop is drawn too tight, it can be loosened by pulling firmly.
The invention also provides methods for attaching soft tissue to bone. In these methods, an anchor of the type described above can be emplaced in bone. The soft tissue is secured by stitching or by catching a portion of the tissue in a loop of suture, which is subsequently tightened. The suture can be tightened or loosened as necessary during deployment, and need not be knotted.
These and other aspects of the invention are evident in the drawings and in the description that follows.